The Impact of Animal Health Status on Greenhouse Gas Emissions from Livestock

Published on 8 July 2014 in Climate, water and energy , Food, health and wellbeing

Introduction

Ruminant livestock production is a key contributor to the rural and national economy of Scotland, as well as the world-renowned Scottish Food and Drink industry.

However, it comes with a well-documented carbon footprint as a result of the greenhouse gas (GHG) emissions associated with enteric methane production and manure management.

The Climate Change (Scotland) Act 2009 sets ambitious emission reduction targets for Scotland and requires all sectors to reduce GHG emissions to mitigate anthropogenic climate change.

One way to do this is to increase the biological efficiency of livestock production, however, this is constrained by animal health status, and especially, production-limiting endemic disease. While the connections between animal health status and carbon footprint appear obvious and intuitive, there are very few studies or data available to support this assumption.

The research described in this briefing report attempts to address some of these knowledge gaps, with a specific focus on sheep health.

Key Points

GHGs produced while an animal is growing become a net loss to the system if the animal dies before its productive value is realised or if the value of that product e.g. a litre of milk, a kg of meat or a healthy lamb or calf, is reduced due to poor animal health status.
Endemic, production-limiting, diseases have a number of negative outcomes, including death or cull of previously healthy animals, reduced liveweight gain, reduced milk yield and quality, reduced fertility, abortion and/or increased waste in the system.

Research Undertaken

Scottish Government-funded Research

The research presented here was funded by the Scottish Government Strategic Research Programme, specifically, Theme 3: Land Use & Climate Change. The work represents three inter-linked studies, the first two focusing on gastrointestinal parasitism in sheep and the third on whole-farm animal health status.

Gastrointestinal Parasitism in Sheep

In the first study, researchers at SRUC housed parasitized and non-parasitised ewes at the College’s ‘GreenCow’ facility, and monitored methane emissions, feed intake and productivity over the course of infection.

Results suggest that ewe parasitism resulted in greater ewe body weight loss and reduced liveweight gain in their lambs for the same level of methane emissions per unit feed intake. This implies that parasitism increases methane output arising from the additional feed intake required to delay weaning to reach the same productive end-point and to replace lost ewe reserves. This equates to a ~14% increase in methane output in ewes. Applying these findings to lambs in grazing systems, parasite driven inefficiencies of production can result in up to 140% increase in methane output.

In the second study, scientists at the Moredun Research Institute modelled the GHGs associated with fat lamb production on the Institute’s farm, under four different anthelmintic (drug) treatment regimes over 5 consecutive grazing seasons.

The respective treatment groups were (1) Monthly – whole flock treatment, (2) Strategic – whole flock treatment based on likely parasite challenge, (3) Clinical signs – whole flock treatments based on the appearance of clinical signs e.g. ill-thrift, scouring or, (4) Targeted Selective Treatment (TST) – individual treatments given to lambs not maintaining calculated production efficiency.

Results showed a significant treatment effect over all years, with the ‘Clinical signs’ group becoming separated from the other 3 treatment groups, as a result of animals taking longer (or failing) to reach target market weight, as in the study above. This represented an average ~10% increase in GHG emissions/kg liveweight gained over a given grazing season compared to the other 3 treatment groups. TST was the preferred option for sustainable parasite control, as it maintains production efficiency and reduces selection for anthelmintic resistance.

Whole-farm Animal Health Status

In the third study, SRUC scientists working at the College’s hill farm at Kirkton, have been establishing baseline GHG measurements sheep under genuine Scottish farming conditions, as a prerequisite for attributing changes in GHG emissions to any specific or general health condition.

There is a complex interaction between animal health, disease, genetics, management practices etc, which ensures that the total effect of animal health on the whole-farm carbon budget is not simply the sum of all the parts.

Hill sheep have proven to be particularly challenging in the context of health and GHGs because of their relatively low productivity, yet any improvements have a much higher ‘gearing’ because of the high proportion of lambs kept for replacements. A small increase in lambs reared leads to a proportionally higher effect on outputs. Inherent animal health and welfare concerns e.g. high lamb and ewe mortality (currently ~7% annually nationally), low life expectancy, poor longevity, and some significant disease issues are problems but have high scope for improvement. Improved productivity (i.e. more meat/kg GHG), increased output of lamb and fewer unproductive animals all contribute.

As an example, analysis of ewe mortality, retention age and replacement rates shows that reducing ewe mortality from 5% to 3% increases lamb output by 14%, alongside the increase in ewe age. Improvements in longevity by an average of an extra year result in many fewer replacement and unproductive females retained and more sold, more productive ewes kept and multiple knock-on effects for GHG emissions overall e.g. 21% reduction in total methane (kg ewe) and 39% reduction in methane per kg lamb sold.

Policy Implications

Reducing ovine parasitism represents a potential win-win-win situation i.e. it reduces the carbon footprint of sheep production systems, increases feed efficiency and improves animal welfare. This work highlights that not all of the parasite driven production inefficiencies (and thus increased GHG emissions) can be recovered through parasite control (i.e. drugs) and that there is a trade-off between slowing the development of drug resistance and reducing the GHGs associated with parasitism, which may change as the climate changes.

The overall implications of this work are that, improving animal health and dealing effectively with endemic, production-limiting disease can help reduce the carbon footprint of livestock farming and livestock products.

Improving animal health and efficiency generally would also be expected to improve the economics of livestock farming, which should in turn encourage uptake of best practice advice for sustainable disease control.

Mortality, poor fertility and poor performance have a major influence on the efficiency of farming systems and their associated emissions metrics.

Farm management is likely to have the greatest overall impact on GHG emissions at the system level but animal health improvements should represent added value and are relatively easy to achieve in the short-to-medium term.

The challenge for policy makers becomes how to translate such emissions savings at the individual, flock/herd or farm level into savings at the national or international scale, to help meet challenging GHG emission reduction targets.